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Engine State Settings Fighting Each Other Causing Craziness

EFI Tuning Fundamentals

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Discussion and questions related to the course EFI Tuning Fundamentals

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I've been getting good results lately dialing in my tune and turned my attention to setting the engine state settings in the Tuner Studio Ultra for the Megasquirt PNP3 ECU. I'm going to need a little guidance here because if I set the parameters the way I believe they need to be set, it creates all sorts of craziness and fighting happening all at once. Here's my parameters and what is happening

Use VSS? = Yes

This is a yes or no, there is no option for anything else so I decided to use the Vehicle Speed Sensor otherwise I don't see how the ECU will know I need to be in closed loop idle for example and not in cruise.

VSS Threshold (MPH) = 20

This is higher than I thought it should be but as I'm coming to a stop if this is set to like 5 or 10 by the time I come to a stop the closed loop idle seems to take too long to kick in so ill come up to a stop sign and im already stopped and the idle still needs a moment to catch up and switch from cruising mode to closed loop idle mode so you have to stand there for a few seconds until the rpm comes down and settles down. If I set this to 20 it feels like the system can do its process of changing from cruise to closed loop before I come to a complete stop and by the time I am fully stopped whatever needed to happen happened and I have a steady good low idle rpm without having to wait for it to come down. I'm assuming the dashpot needs a couple seconds to let the rpm come down. This is not really a problem for me, 20 works ok and I think its fine for my setup.

Slow Acceleration Threshold (rpm/sec)

This is where things start to get crazy. The directions say to have this value as low as possible so that it catches all the acceleration but not so low to where it catches "RPM Jitter". I guess I should start by asking how slow of an acceleration? If it means slow acceleration as in just normally driving and accelerating to get down the street then for my that would be around 100RPM. I put that value in and test it and it changes the engine state from cruise to accelerate. This seems fine until you are idling where if your rpm oscillates a bit at idle it kicks you out of closed loop idle and into acceleration and back and forth because now it's fighting for what engine state its in. I really wish there was a way to type in like a minimum RPM where this becomes active because even if you are idling and you rev up the engine it automatically kicks it out of closed loop idle and this fight begins between closed loop idle, accelerate and in the next section also the deceleration. It would be really nice if there was a setting where I could type in that anything below like 1,200RPM is to always be considered idle to avoid this issue.

Slow Deceleration Threshold (rpm/sec)

This is similar to the above but this is for deceleration. It says to set this cruise in a high gear and see what RPMdot value you get by lifting off the throttle and decelerating. For me this value was about -100 RPM so I put that in and it worked fine when I was actually decelerating. While the car is moving these settings would switch between Acceleration to Cruise to Deceleration and Overrun. I felt like I had it dialed in until I came to a stop and all of the engine state settings would fight each other at the same time causing the engine to do all sorts of erratic idling and rpm oscillations.

In order to make the engine states fight each other I need to raise the slow acceleration and slow deceleration to at like 600 and -600 on the deceleration which basically then makes the engine states not even work. All I get then is either closed loop idle or cruise and then overrun when changing gears but no acceleration or deceleration engine states. How are you guys setting this so that it picks up the acceleration and deceleration but doesn't cause problems with the closed loop idle?

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